﻿namespace Terminal.Gui.Views;

/// <summary>Implementation of <see cref="ITreeBuilder{T}"/> that uses user defined functions</summary>
public class DelegateTreeBuilder<T> : TreeBuilder<T>
{
    private readonly Func<T, bool> canExpand;
    private readonly Func<T, IEnumerable<T>> childGetter;

    /// <summary>
    ///     Constructs an implementation of <see cref="ITreeBuilder{T}"/> that calls the user defined method
    ///     <paramref name="childGetter"/> to determine children
    /// </summary>
    /// <param name="childGetter"></param>
    /// <returns></returns>
    public DelegateTreeBuilder (Func<T, IEnumerable<T>> childGetter) : base (false) { this.childGetter = childGetter; }

    /// <summary>
    ///     Constructs an implementation of <see cref="ITreeBuilder{T}"/> that calls the user defined method
    ///     <paramref name="childGetter"/> to determine children and <paramref name="canExpand"/> to determine expandability
    /// </summary>
    /// <param name="childGetter"></param>
    /// <param name="canExpand"></param>
    /// <returns></returns>
    public DelegateTreeBuilder (Func<T, IEnumerable<T>> childGetter, Func<T, bool> canExpand) : base (true)
    {
        this.childGetter = childGetter;
        this.canExpand = canExpand;
    }

    /// <summary>Returns whether a node can be expanded based on the delegate passed during construction</summary>
    /// <param name="toExpand"></param>
    /// <returns></returns>
    public override bool CanExpand (T toExpand) { return canExpand?.Invoke (toExpand) ?? base.CanExpand (toExpand); }

    /// <summary>Returns children using the delegate method passed during construction</summary>
    /// <param name="forObject"></param>
    /// <returns></returns>
    public override IEnumerable<T> GetChildren (T forObject) { return childGetter.Invoke (forObject); }
}
